The present invention generally relates to a storage system and a data management method, and is in particular suitable for application in a storage system where an AOU (Allocation On Use) function is provided to a storage apparatus to become a copy source, and the AOU function is not provided to a storage apparatus to become a copy destination in remote copying.
In recent years, pursuant to the development of the information society, the data volume of user data stored by users in a storage apparatus is increasing sharply, and customer needs relating to increase in capacity and improvement in usage efficiency of storage apparatuses are also increasing from the perspective of cost reduction.
Under the foregoing circumstances, in recent years, the AOU function is being proposed as one function of a storage apparatus (refer to Japanese Patent Laid-Open Publication No. 2005-11316). The AOU function is a function for presenting to a host system a virtual volume as a logical volume (hereinafter referred to as a “primary volume”) for reading and writing user data, and dynamically allocating to the primary volume a real storage extent for actually storing user data according to the usage of such primary volume. According to this kind of AOU function, it is possible to efficiently use the storage extent in the storage apparatus while presenting to the host system the volume of the capacity upward of the storage extent in the storage apparatus.
Further, as another function of a storage apparatus, there is a remote copy function (refer to Japanese Patent Laid-Open Publication No. 2003-122509). The remote copy function is a function of duplicating and retaining user data written in the primary volume of one's own storage apparatus by copying such user data to a volume (hereinafter referred to as a “secondary volume”) in another storage apparatus installed at a remote location on the one hand, and restoring the primary volume using backup data retained in the secondary volume when the user data in the primary volume is lost due to disaster or the like on the other hand. According to this kind of remote copy function, it is possible to create a highly reliable storage system.